1. Field of the Invention
The present invention relates to an automotive headlamp apparatus used for vehicles and the like and a method for controlling the automotive headlamp apparatus.
2. Brief Description of Related Art
Generally, an automotive headlamp apparatus is capable of switching an illumination mode between a lower beam (low beam) and an upper beam (high beam). A lower beam is for illuminating an area close to, for example, a vehicle with a predefined intensity. Distribution of a lower beam is subject to provisions that provide for prevention of glare as experienced by oncoming vehicles or vehicles in front. A lower beam is primarily used on city streets. On the other hand, an upper beam is for illuminating wide areas ahead and distant areas with a relatively high illumination intensity. An upper beam is primarily used for high-speed driving on a road with relatively few oncoming vehicles and vehicles in front. As a result, the upper beam enhances the visibility of a driver much greater than the lower beam. However, an upper beam has a disadvantage of causing the driver of a vehicle or pedestrian ahead of the illuminating vehicle to experience a glare.
In the light of this, a technique is proposed where the light distribution in an upper beam region is varied. Disclosed in Japanese Patent Application Publication No. 2008-37240 is an automotive headlamp wherein when an illumination-prohibited object exists in any of a plurality of upper beam illumination areas, an upper beam unit, for use in an upper beam illumination area where the illumination-prohibited object lies in a plurality of upper beam units, is turned off.
The degree of glare experienced by a driver who drives a vehicle in front of a driver's own vehicle, which travels with high beam selected, changes with the distance. In view of this fact, Japanese Patent Application Publication No. 2000-233684 or Japanese Patent Application Publication No. Hei07-101291 discloses a headlamp apparatus that controls the glare in a manner such that a cut line is moved or the illumination of lamp is controlled in accordance with the position of a vehicle in front.
The above-described techniques are applied with a view to reducing the glare. Further reduction of the glare is desired in order to enhance the visibility.